Having photos taken being stored in-app and possibly being able to put it in the camera roll?

To save some trouble or worry to some users, it could be possible to store pictures tooken in-app so that they can view it later possibly offline and so that it can be uploaded later if for example no internet is available. But, that also leads into another idea I have in mind, having the option to add taken pictures into the camera roll and even possibly downloading other users' images into the iDevice's camera roll. It would be a nice and convenient use so that users can show other people the pictures they took and what it possibly would look like if effects were added.